Structural effects on the oxygen reduction reaction (ORR) have been studied on the low index planes of rutile TiO 2 doped with Nb (0.05-1 wt%) in 0.1 M HClO 4. The order of the ORR activity at 0.20 V (vs. RHE) is TiO 2 (100) < TiO 2 (111) < TiO 2 (110), and the activity increases with increasing Nb concentration. The activity of TiO 2 (110) is 5.6 times as high as that of TiO 2 (100) at Nb concentration 1%. The order of the ORR activity does not correlate with the amount of oxygen vacancy defects that are known as the active sites of the ORR of TiO 2 nanoparticles. The ORR activity of 1%Nb-doped TiO 2 (100) modified with melamine is 2.1 times higher than that of the unmodified one. The activity of 1%Nb-doped TiO 2 (110) modified with melamine is the highest in the low index planes of TiO 2. Modification by tetra-n-hexylammonium cation (THA +) affects the ORR activity slightly.